A Special Comet Makes Grand Return to NASA Spacecraft's Field of View

A special comet just made its grand return to the view of one of NASA's sun-gazing spacecraft. Comet 96P/Machholz was caught on camera by the Solar and Heliospheric Observatory (SOHO), which is co-managed by the European Space Agency.

A picture from Oct. 25 shows Comet 96P in the bottom-right corner of the image, exactly as predicted. The comet made its way up the right-hand side of the spacecraft's field of view before disappearing out of sight on Monday (Oct. 30). A composite image of the comet's travels released Friday (Oct. 27) showcases that flyby.

This composite image shows the approach of Comet 96P/Machholz around the sun between Oct. 25 and 27 as seen by the NASA/ESA Solar and Heliospheric Observatory in space. The comet is making its fifth trip around the sun in 2017 that SOHO has witnessed.

Credit: Composite image provided by Barbara Thompson (NASA)

"In years past, comet 96P has produced some beautiful images from SOHO's imagers," reads a statement on SOHO's page. "Its passage in 2002 was perhaps the most stunning so far, with a bonus coronal mass ejection, or CME, erupting just a few hours after the comet passed the sun." (A CME is a burst of charged particles from the sun that is often associated with solar flares.)

"It's worth noting that there was no link between the two — we sometimes see as many as six more CMEs in a day, so it's no surprise to see a comet at the same time," the SOHO statement added. "But nonetheless, it makes for a beautiful display! This time around it won't look quite so spectacular, but with an estimated peak magnitude of +2, it will still be very bright."

Comet 96P was discovered by amateur astronomer Don Machholz in 1986, and it orbits the sun every 5.24 years. Its closest approach to the sun is about three times closer than the distance between the sun and Mercury, at 11 million miles (18 million kilometers) or just over one-tenth the distance between the Earth and the sun.

SOHO itself is a prolific comet gazer, even though its primary mission is to observe the sun's behavior and make better predictions about when solar activity will affect Earth. Since its launch in December 1995, it has spotted well over 3,000 comets.

Comet 96P/Machholz is shown (lower right) in the view of the Solar and Heliospheric Observatory (SOHO) on Oct. 25, 2017. The spacecraft uses a device to block out the light of the sun, which gives it a better view of solar activity (and, coincidentally, sun-grazing comets).

Credit: NASA/ESA/SOHO

During this flyby, for the first time, 96P will be seen by both SOHO and another spacecraft at the very same time. NASA's STEREO-A (Solar and Terrestrial Relations Observatory Ahead) spacecraft will observe the comet from nearly the opposite side of Earth's orbit. The comet should appear in the spacecraft's field of view between Saturday (Oct. 28) and Monday.

Comets are debris left over after the solar system formed 4.6 billion years ago. Let's see what you know about these ancient and elusive celestial wanderers.

Elizabeth Howell is a contributing writer for Space.com who is one of the few Canadian journalists to report regularly on space exploration. She is pursuing a Ph.D. part-time in aerospace sciences (University of North Dakota) after completing an M.Sc. (space studies) at the same institution. She also holds a bachelor of journalism degree from Carleton University. Besides writing, Elizabeth teaches communications at the university and community college level. To see her latest projects, follow Elizabeth on Twitter at @HowellSpace.